Roll form apparatus, method to manufacture crush tubes

ABSTRACT

An apparatus comprises an uncoiling device for unrolling sheet material, an embossing device for embossing a series of crush initiating embossments into the sheet, a slitter to remove deformed edges of the sheet to facilitate welding, and a roll former with rolls configured to deform the sheet into a continuous tubular beam with walls each including some of the embossments, with the rolls being configured to clear the embossments but accurately form corners joining the walls. The apparatus further includes a welder welding abutting edges of the sheet together to fix the tubular beam, with the abutting edges being located inboard of an adjacent one of the corners but outboard of an outboard edge of adjacent ones of the embossments, and a cutoff device for cutting the continuous tubular beam into beam segments. A related method is also disclosed.

This application claims priority under 35 USC section 119(e) of U.S. Provisional Patent Application Ser. No. 61/838,583, filed on Jun. 24, 2013, entitled ROLL FORM APPARATUS, METHOD TO MANUFACTURE CRUSH TUBES, the entire disclosure which is hereby incorporated by reference in its entirety.

BACKGROUND OF THE INVENTION

The present invention relates to a roll form apparatus and method to form sheet material into an elongated tubular beam of generally uniform cross section, but where the tubular beam has lateral deformations forming crush initiators in side walls of the beam to intentionally affect longitudinal impact strength of the beam and to intentionally create both a high strength initial resistance to impact but also a collapse that is predictable and that insures multiple bending locations for optimal impact energy absorption. The present invention also includes crush tubes manufactured by roll forming apparatus, and that are used to mount a bumper reinforcement beam to vehicle side frame rails.

Roll forming apparatus and processes include forming rolls that are well adapted to form sheets of very high strength material into tubes at relatively high speed and with good dimensional consistency. The forming rolls provide opposing rolling contact against the sheet when deforming the sheet. As a result, the forming rolls can be made durable for long service life (i.e. more parts can be made prior to wear causing a need for refurbishing the forming rolls). A problem with roll forming is that it is not typically used for elongated products having longitudinally non-uniform cross sections, because the longitudinally non-uniform cross sections would interferingly engage the forming rolls.

Stamping processes utilize opposing dies that “pound” against each other to form sheet material. A problem is that, when the sheet is high strength, stamping dies tend to wear relatively quickly, such that they require constant maintenance and refurbishing.

Crush tubes are often used to mount bumper reinforcement beams to vehicle frame rails. The crush tubes extend longitudinally of the vehicle, and must be sufficiently strong to support a bumper beam, but preferably include crush initiators so that the tubes collapse predictably and consistently during a vehicle impact in a longitudinal direction in a multi-point crumpling manner providing a maximum amount of energy absorption. Sometimes, crush tubes are made of higher strength materials to allow thinner walls for reduced weight. However, higher strength and thinner materials have an even greater need for crush initiators to prevent pre-mature catastrophic collapse and to facilitate multi-point crumpling for good energy absorption.

Historically, crush tubes are stamped components, such as two-piece clam shell designs welded together, since this allows consistent placement and formation of crush initiators in side walls of the crush tubes, and allows a high degree of design freedom. For example, see Hirano U.S. Pat. No. 4,272,114 (FIG. 13). Historically, crush tubes are not roll formed, since the existence of crush initiators require a manufacturing process capable of making non-uniform cross sections. Heatherington U.S. Pat. No. 7,617,916 does disclose a crush tube that is initially roll formed with longitudinal channels and then finally formed in a secondary operation by expanding portions of the channels. However, the tube in Heatherington requires substantial secondary processing to expand the roll formed tube, with the secondary processing requiring considerable cycle time and also placing stress on any welded areas during expansion.

A roll form apparatus and method of making crush tubes is desired, and also a roll formed crush tube is desired that is capable of being made on a roll form apparatus and method, where the process is simple, reliable, and does not require substantial secondary processes, and further where the crush tube minimizes weight and cost of manufacture, including minimal secondary processing.

BRIEF SUMMARY OF THE INVENTION

In one aspect of the present invention, a roll form apparatus comprises an unroller device for unrolling an elongated sheet of material from a roll of the material, an embossing device for embossing a series of crush initiating embossments into the sheet, and a roll former with rolls configured to deform the sheet into a continuous tubular beam defined by walls, each wall defining a plane with some of the embossments extending from the plane in at least one of the walls, the walls being joined by corners with the embossments spaced from the corners. The apparatus further includes a welder welding abutting edges of the sheet together to fix the tubular beam, with the abutting edges being located inboard of an adjacent one of the corners but outboard of an outboard edge of adjacent ones of the embossments, and a cutoff device for cutting the continuous tubular beam into beam segments with the beam segments being substantially finally formed as crush initiator tubes.

In a narrower form, the apparatus includes a slitter to trim edges of the sheet prior to roll forming in order to eliminate distortion of the edges from the embossing device.

In a narrower form, the cutoff device includes a cutoff blade that cuts one end of the beam segments at an angle different than 90 degrees to a longitudinal length of the tubular beam.

In another aspect of the present invention, a method includes unrolling an elongated sheet of material from a roll of the material; embossing a series of crush initiating embossments into the sheet; roll forming to form the sheet into a continuous tubular beam defined by walls, each wall defining a plane with some of the embossments extending from the plane in at least one of the walls, the walls being joined by corners with the embossments spaced from the corners; welding abutting edges of the sheet together to fix the tubular beam, with the abutting edges being located inboard of an adjacent one of the corners but outboard of an outboard edge of adjacent ones of the embossments; and cutting the continuous tubular beam into beam segments, with the beam segments being substantially finally formed as crush initiator tubes.

In a narrower form, the method includes a step of slitting edges of the sheet after embossing and prior to roll forming in order to eliminate distortion of the edges from the embossing step.

In another aspect of the present invention, a roll form apparatus includes an embossing device for embossing a series of crush initiators into the sheet, a roll former with rolls configured to deform the sheet into a continuous tubular beam defined by walls, the walls being joined by corners with the crush initiators spaced from the corners, the rolls being configured to avoid contact with portions of the sheet having the crush initiators placed therein, a welder welding edges of the sheet together at a location inboard of the corners but outboard of an outboard edge of adjacent ones of the crush initiators, and a cutoff device for cutting the continuous tubular beam into crush tubes.

In another aspect of the present invention, a crush tube product made by a roll form process comprises a sheet having opposing edges that is deformed to have embossed crush initiators and that is roll formed into a tubular shape and cut to length for use as a crush tube for mounting a bumper beam on a vehicle front end. The crush initiators are formed perpendicularly into the sheet inboard of the opposing edges, and the elongated tubular shape has a longitudinal centerline caused by roll forming the sheet so that the opposing edges abut, with the tubular shape having a constant cross section except for the crush initiators, the constant cross section having side walls defining corners. A weld secures the opposing edges together to fix the elongated tubular shape, with some of the crush initiators being between the weld line and an adjacent one of the corners. A section of the elongated tubular shape is cut into a desired length to thus form a crush tube configured to support a bumper beam on a vehicle frame and configured to longitudinally crush with a predictable force/deflection curve when impacted parallel the longitudinal centerline.

These and other features, advantages, and objects of the present invention will be further understood and appreciated by those skilled in the art by reference to the following specification, claims, and appended drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view of a vehicle frame with crush tubes mounting a bumper reinforcement beam to the vehicle frame rail tips, the crush tubes being roll formed and including embossed crush initiators on side walls.

FIG. 1A is a perspective view of the roll formed beam in FIG. 1A, including showing a beam segment cut from the end of the beam to form the crush tube of FIG. 1 and also showing dashed lines representing a second beam segment ready to be cut.

FIG. 1B is a fragmentary perspective view of the roll formed continuous beam after the welder in FIG. 1A.

FIGS. 1C and 1D are cross sections taken at locations 1C and 1D in FIG. 1A.

FIG. 2 is an enlarged perspective view of the crush tube in FIG. 1.

FIGS. 3-5 are perspective views of modified crush tubes similar to FIG. 2.

FIG. 6 is a perspective view of a bumper reinforcement beam mounted by crush tubes to vehicle frame rail tips.

FIGS. 7-8 are front and rear perspective views of the crush tubes in FIG. 6.

FIG. 9 is a schematic top view of a bumper system not unlike FIG. 6, including a bumper reinforcement beam mounted by crush tubes to vehicle frame rail tips.

FIG. 10 is a schematic top view of the roll formed tubular continuous beam in FIG. 1A, with angled cutting planes overlaid on the continuous beam to show how adjacent portions of the continuous beam are cut to form similar but “180-degree flipped” crush tubes.

FIG. 11 is a perspective view of a crush tube having a partial internal leg supporting sidewalls of the crush tube.

FIG. 12 is a graph showing a force-deflection curve for the crush tube shown in FIG. 11.

FIGS. 13 and 14 are perspective and cross sectional views of a modified crush tube.

DETAILED DESCRIPTION

A bumper system 10 (FIG. 1) includes a frame with side rails 11 (sometimes called or including “frame rail tips”), a high-strength swept tubular bumper reinforcement beam 12, and two crush tubes 41 supporting the beam 12 on the side rails 11. The bumper system 10 is typically covered by a colored fascia (not specifically shown) for aesthetics.

An apparatus 20 (FIG. 1A) comprises an uncoiling device 21 for unrolling an elongated sheet 22 of coiled material, an embossing device 23 (e.g. reciprocating stamping device with dies, or forming rolls with mating protrusions and recesses) for repeatedly embossing a series of crush initiating embossments 24 into the sheet, optionally a slitter 23A (at a downstream end of the embossing device 23) for trimming sheet edges back to a straight line (which is needed when the sheet's edges are distorted, i.e. “sucked in”, when forming the embossments into the sheet), trimming edges of the unrolled sheet that are and a roll former 25 with stations having opposing forming rolls 26 configured to deform the sheet into a continuous tubular beam 27 (FIG. 1B) with walls 28-31 each including some of the embossments, with the rolls 26 being configured to clear the embossments 24 but accurately form corners 32 joining the walls.

The apparatus 20 (FIG. 1A) further includes a welder 33 with welding tip 33A welding a weld bead 34 to bond aligned abutting edges 35-36 of the sheet together to fix a cross section of the tubular beam 27. It is noted that a welding tip 33A is illustrated, but it is contemplated that any type welding can be used, including an induction welding process or laser welding process (neither of which use a weld tip per se). The abutting edges 35-36 are coplanar and located inboard of an adjacent one of the corners 32 but outboard of an outboard edge of adjacent ones of the embossments 24, and a cutoff device 37 is positioned for cutting the continuous tubular beam 27 into beam segments 38 as it exits the roll form apparatus. Notably, the slitter is used when the edges are so distorted by the embossments that the edges don't abut properly unless the edges are re-trimmed. A wall-trimming device 39 is provided in a secondary operation, and is configured to form a longitudinally-extending flange 40 on an end of the segment 38 to finally form the crush tube 41. Notably, the embossments 24 can be any shape and depth. The cross section of the illustrated crush tube 41 is orthogonal (i.e square or rectangular), and the embossments 24 all extend inward of the tubes.

The illustrated welder 33 (FIG. 1A) includes internal and external mandrels 42-43 (FIG. 1D) that support a cross sectional shape of the beam 27, holding the abutting aligned edges together in a coplanar condition during the welding process. It is noted that the weld is offset from a centerline of the beam 27 so that the welding line avoids the crush initiator embossments 24. Further, the internal mandrels 42 (anchored upstream by a cable 42A secured at anchor 42B) include channels and/or clear-outs (see FIG. 1C) so that they do not interferingly engage and reform the embossments 24. Notably, the edges 35-36 are preferably abutting and coplanar in order to avoid a double-thickness wall portion, which double-thickness wall portion may unacceptably cause a strong corner to the crush tube 41.

As noted above, the crush tube 41 (FIG. 2) includes four walls 28-31 connected by radiused corners 32. The illustrated walls 28 and 30 are slightly longer in width than walls 29 and 31, such that the crush tube 41 forms a rectangular shell shape. The walls 28 and 30 each include two crush initiating embossments 24 that are elongated in a longitudinal direction to be about twice as long as wide. The flanges 40 extend coplanar from walls 28 and 30. The walls 29 and 31 each include three crush initiating embossments 24 that are elongated in a lateral direction to be about three times as long as wide. A preferred depth of the illustrated embossments 24 is about 1-3 times a thickness of the material forming the walls 28-31, though it is contemplated that the depth can be more or less deep. The weld bead 34 is located outboard of an adjacent embossment 24, but is located on a flat portion of the wall (i.e. offset from the radiused corner).

It is contemplated that the material used for the crush tube can be a variety of different thicknesses and material strengths, depending on the functional requirements of a particular application. For example, the illustrated material of crush tube 41 can be 1.0-3.0 mm thick, or more preferably about 1.2-1.6 mm thick. The material is preferably steel having a tensile strength of at least about 50 KSI, or higher tensile strengths of 120 KSI or higher. The embossments 24 are all illustrated as extending inward, but it is contemplated that some or all of them could be designed as extending outward, as shown in FIG. 4, and that they can be different shapes, as shown in FIG. 5.

FIGS. 3-14 are perspective views of modified crush tubes similar to FIG. 2. Similar features, characteristics and aspects are identified using the same numbers, but adding a letter “A” or “B” or etc. This is done to reduce redundant discussion.

FIG. 3 illustrates a crush tube 41A similar to crush tube 41, but crush tube 41A has 45 degree “flat/angled” corners 32A (rather than fully radiused corners 32 as in crush tube 41). Further, the embossments 24A in crush tube 41A all are elongated laterally, three embossments 24A being on each side wall 28A-31A. Also, flanges (40) are eliminated, with both ends being perpendicularly trimmed. Also, a cross section of the crush tube 41A is modified to match a corresponding shape of the mating frame rail tip on the vehicle. It is contemplated that one of the ends can be trimmed at an angle to fully engage a swept reinforcement beam (see FIG. 1).

FIG. 4 illustrates a crush tube 41B that is similar to crush tube 41, but crush tube 41B only includes embossments 24B on two opposing side walls 29B and 31B, and does not include any embossments on the other side walls 29B and 31B. Crush tube 41B does include flanges 40B.

FIG. 5 illustrates a crush tube 41C that is similar to crush tube 41B, but the embossments 24C are shaped to form non-uniform channels. For example, two embossments 24C are illustrated, one being a T-like shape, and one being an X-like shape.

FIG. 6 is a perspective view of a bumper reinforcement beam 12E mounted by crush tubes 41E to brackets on the vehicle frame rail tips 11E. A lower pedestrian impact bar 14 mounts to brackets 15 extending vertically from the beam 12E. FIGS. 7-8 are front and rear perspective views of the crush tubes 41E. Notably, a rear end of the crush tubes 41E is cut square (i.e. at 90 degrees to a length of the crush tube), but the front end is cut at an angle to the length of the crush tube (so that walls 29E and 31 E stablyl abut a rear surface of a longitudinally swept beam 12E). (See FIG. 6 and also FIGS. 9-10.) Also, one or both of the ends of the crush tubes 41E are cut to include features that locate and orient the crush tube 41E on the bumper beam 12E and/or on the frame rail tip, and that facilitate fastener attachment or welding. As illustrated in FIG. 10, by cutting the continuous roll formed beam first with a square cut and then with an angled cut, successive beam segments cut to a final shape of the crush tubes 41E with less wasted material, since a “long side” (D1) of successive beam segments alternates between high and low positions on the continuous beam.

FIG. 11 is a perspective view of a crush tube 41F having a partial-length internal leg 49F supporting sidewalls of the crush tube. It is noted that the internal leg 49F only extends a short distance longitudinally, such that it does not add significant weight to the crush tube 41F. Each end of the internal leg 49F has a flange 49F′ that is secured to the opposing walls of the crush tube. The flanges 49F′ of the internal leg 49F can be attached by welding, adhesive, or other means. By making the internal leg 49F from a relatively narrow strip, it helps minimize weight. At the same time, the internal leg 49F provides stability to the side walls, even when the internal leg is a relatively thin material, such as only 1.0 mm thick or less, and when the leg 49F has only a limited width, such as only 2-4 mm width. Also, the channel 24F′ is formed in each wall 28F-31F, and replaces the stamped embossments (24).

FIG. 12 is a graph showing a force-deflection curve for the crush tube shown in

FIG. 11. The graph illustrates that the present roll formed crush tube 41F provides surprisingly good strength and energy absorption during a length of its crush stroke along an impact longitudinally aligned with a centerline of the crush tube 41F and into the frame rail to which it is attached.

FIGS. 13 and 14 are perspective and cross sectional views of a modified crush tube 41G. The crush tube 41G includes an internal leg 49G similar to FIG. 11, but in FIGS. 13-14, the internal leg 49G extends a length of the crush tube 41G. This allows the crush tube 41G to be made from a single sheet of material, as shown in FIG. 14. Edges of the sheet are folded into abutting contact and welded to other parts of the sheet to form two tubes, with the internal leg forming a common center leg. It is contemplated that the single sheet for forming the crush tube 41G can include adjacent strips (welded together prior to roll forming) of different material properties and different thicknesses. For example, the partial strip of material in the original sheet that ends up forming the internal leg could be a much thinner and/or weaker and/or cheaper material than the remaining portions of the sheet forming the two tubes. This arrangement allows crush tubes to be made in a roll former while minimizing secondary processing, and optimizing material location and weight, yet without making a center of the crush tube 41G being undesirably strong (i.e. and hence wasting material and leading to excess weight).

It is believed to be surprising and unexpected to produce a bumper crush tube by roll forming without substantial additional secondary processing, since roll forming tends to produce a beam of constant cross section. Yet the present crush tube product is made by a roll form process without substantial secondary processing. Specifically, a sheet having opposing edges is deformed to have embossed crush initiators and is then roll formed into a tubular shape and cut to length for use as a crush tube for mounting a bumper beam on a vehicle front end. The crush initiators are formed perpendicularly into the sheet inboard of the opposing edges, and the elongated tubular shape has a longitudinal centerline caused by roll forming the sheet so that the opposing edges abut, with the tubular shape having a constant cross section except for the crush initiators, the constant cross section having side walls defining corners. A weld secures the opposing edges together to fix the elongated tubular shape, with some of the crush initiators being between the weld line and an adjacent one of the corners. A section of the elongated tubular shape is cut into a desired length to thus form a crush tube configured to support a bumper beam on a vehicle frame and configured to longitudinally crush with a predictable force/deflection curve when impacted parallel the longitudinal centerline.

It is to be understood that variations and modifications can be made on the aforementioned structure without departing from the concepts of the present invention, and further it is to be understood that such concepts are intended to be covered by the following claims unless these claims by their language expressly state otherwise. 

The invention claimed is:
 1. A roll form apparatus comprising: an uncoiler device for unrolling an elongated sheet of material from a roll of the material; an embossing device for embossing a series of crush initiating embossments into the sheet; a roll former with rolls configured to deform the sheet into a continuous tubular beam defined by walls, each wall defining a plane with some of the embossments extending from the plane in at least one of the walls, the walls being joined by corners with the embossments spaced from the corners; a welder welding abutting edges of the sheet together to fix the tubular beam, with the abutting edges being located inboard of an adjacent one of the corners but outboard of an outboard edge of adjacent ones of the embossments; a cutoff device for cutting the continuous tubular beam into beam segments, with the beam segments being substantially finally formed as crush tubes.
 2. The apparatus of claim 1, including an end trimmer between the embossing device and the roll former to trim edges of the sheet that are deformed when forming the crush initiating embossments.
 3. The apparatus of claim 1, including a wall-trimming device that shortens some of the walls but leaves a longitudinally-extending flange on at least one of the walls.
 4. The apparatus of claim 1, wherein the embossing device forms embossments in each of the walls, and wherein the rolls are configured to clear the embossments when deforming the sheet.
 5. A method comprising: uncoiling an elongated sheet of material from a roll of the material; embossing a series of crush initiating embossments into the sheet; roll forming deform the sheet into a continuous tubular beam defined by walls, each wall defining a plane with some of the embossments extending from the plane in at least one of the walls, the walls being joined by corners with the embossments spaced from the corners; welding abutting edges of the sheet together to fix the tubular beam, with the abutting edges being located inboard of an adjacent one of the corners but outboard of an outboard edge of adjacent ones of the embossments; cutting the continuous tubular beam into beam segments, with the beam segments being substantially finally formed as crush tubes.
 6. The method of claim 5, including a step of trimming edges of the sheet between the steps of embossing and roll forming, the step of trimming eliminating deformed portions of the sheet caused when the crush initiating embossments are formed.
 7. A roll form apparatus comprising: an embossing device for embossing a series of crush initiators into a sheet; a roll former with rolls configured to deform the sheet into a continuous tubular beam defined by walls, the walls being joined by corners with the crush initiators spaced from the corners, the rolls being configured to avoid contact with portions of the sheet having the crush initiators placed therein; a welder welding edges of the sheet together at a location inboard of the corners but outboard of an outboard edge of adjacent ones of the crush initiators; and a cutoff device for cutting the continuous tubular beam into crush tubes.
 8. A crush tube product made by a roll form process comprising: a sheet having opposing edges that is deformed to have embossed crush initiators and that is roll formed into a tubular shape and cut to length for use as a crush tube for mounting a bumper beam on a vehicle front end; the crush initiators being formed perpendicularly into the sheet inboard of the opposing edges; the elongated tubular shape having a longitudinal centerline caused by roll forming the sheet so that the opposing edges abut, with the tubular shape having a constant cross section except for the crush initiators, the constant cross section having side walls defining corners; a weld securing the opposing edges together to fix the elongated tubular shape, with some of the crush initiators being between the weld line and an adjacent one of the corners; and a section of the elongated tubular shape being cut into a desired length to thus form a crush tube configured to support a bumper beam on a vehicle frame and configured to longitudinally crush with a predictable force/deflection curve when impacted parallel the longitudinal centerline. 